Bioenergetics is the study of _______ in biological systems.
Bioenergetics is the study of energy flow and transformations in biological systems.
Biological systems cannot extract usable energy from _______ because cellular temperature is _______.
Biological systems cannot extract usable energy from heat diffusion because cellular temperature is higher than the surroundings.
Living organisms extract energy by _______.
Living organisms extract energy by chemical transformations (oxidation–reduction reactions).
The flow of energy determines _______.
The flow of energy determines whether molecular transformations occur and to what extent.
Chemotrophs obtain energy by _______.
Chemotrophs obtain energy by oxidizing organic molecules.
Humans are _______.
Humans are chemotrophs.
Phototrophs convert _______ into _______.
Phototrophs convert radiant solar energy into chemical energy.
In humans, energy-containing nutrients include _______.
In humans, energy-containing nutrients include carbohydrates, fats, and proteins.
Catabolism is _______ and produces _______.
Catabolism is oxidative and produces ATP, NADH, NADPH, and FADH₂.
Anabolism is _______ and _______.
Anabolism is reductive and consumes ATP.
Final products of catabolism include _______.
Final products of catabolism include CO₂, H₂O, and NH₃.
ATP links catabolism to anabolism by serving as _______.
ATP links catabolism to anabolism by serving as the cell’s energy currency.
Enthalpy (ΔH) represents _______.
Enthalpy (ΔH) represents heat content.
Entropy (ΔS) measures _______.
Entropy (ΔS) measures randomness or disorder.
Free energy (ΔG) represents _______.
Free energy (ΔG) represents energy available to do work.
Only _______ can be used to perform biological work.
Only free energy can be used to perform biological work.
The First Law of Thermodynamics states that _______.
The First Law of Thermodynamics states that energy is conserved.
Energy can be _______.
Energy can be transformed but not created or destroyed.
The Second Law of Thermodynamics states that systems tend toward _______.
The Second Law of Thermodynamics states that systems tend toward increased entropy.
Spontaneous processes proceed toward _______.
Spontaneous processes proceed toward greater disorder.
For spontaneity: _______.
For spontaneity: ΔS(system) + ΔS(surroundings) > 0.
The Gibbs–Helmholtz equation is: _______.
The Gibbs–Helmholtz equation is: ΔG = ΔH − TΔS.
ΔG integrates _______ into one criterion.
ΔG integrates enthalpy and entropy into one criterion.
ΔG predicts _______.
ΔG predicts spontaneity and work potential.
If ΔG = 0, the system is at _______.
If ΔG = 0, the system is at equilibrium.
If ΔG < 0, the reaction is _______.
If ΔG < 0, the reaction is spontaneous (exergonic).
If ΔG > 0, the reaction is _______.
If ΔG > 0, the reaction is nonspontaneous (endergonic).
Spontaneity is determined by _______, NOT ΔG°.
Spontaneity is determined by ΔG, NOT ΔG°.
ΔG° is measured at _______.
ΔG° is measured at 25°C, 1 atm, 1 M concentrations.
ΔG°′ (biological standard) assumes: _______
ΔG°′ (biological standard) assumes: constant pH (~7.0)
_______} is another assumption of ΔG°′.
constant water concentration} is another assumption of ΔG°′.
In biological systems, _______.
In biological systems, ΔG°′ is often treated as equivalent to ΔG.
The relationship between free energy and equilibrium is: _______.
The relationship between free energy and equilibrium is: ΔG = ΔG°′ + RT ln Q.
At equilibrium: _______ and _______.
At equilibrium: ΔG = 0 and Q = Keq.
If products > reactants, lnQ is _______.
If products > reactants, lnQ is positive.
If reactants > products, lnQ is _______.
If reactants > products, lnQ is negative.
Free energy changes are additive, and total ΔG of a pathway equals _______.
Free energy changes are additive, and total ΔG of a pathway equals the sum of individual ΔG values.
A pathway is spontaneous if _______.
A pathway is spontaneous if overall ΔG is negative.
Most metabolic pathways contain _______ that drive the pathway.
Most metabolic pathways contain few highly exergonic steps that drive the pathway.
Glycolysis contains _______.
Glycolysis contains 10 enzymatic steps.
Strongly exergonic steps in glycolysis include: _______, _______, _______.
Strongly exergonic steps in glycolysis include: Hexokinase, Phosphofructokinase-1, Pyruvate kinase.
Overall ΔG°′ for glycolysis is approximately _______.
Overall ΔG°′ for glycolysis is approximately −21 kcal/mol.
ATP consists of _______.
ATP consists of adenine, ribose, and three phosphate groups.
High-energy bonds exist between _______.
High-energy bonds exist between β–γ and α–β phosphates.
ATP hydrolysis releases approximately _______.
ATP hydrolysis releases approximately −7.3 kcal/mol.
P is a _______ because of _______.
P is a high-energy compound because of electrostatic repulsion and resonance stabilization.
ATP is _______, not stored.
ATP is rapidly turned over, not stored.
ATP half-life in resting adults is _______.
ATP half-life in resting adults is ~1 minute.
ATP is consumed by _______, _______, _______, and _______.
ATP is consumed by biosynthesis, muscle contraction, active transport, and thermogenesis.
Compounds with ΔG°′ more negative than ATP can _______.
Compounds with ΔG°′ more negative than ATP can phosphorylate ADP.
Examples of high-energy phosphate compounds include _______ and _______.
Examples of high-energy phosphate compounds include Phosphoenolpyruvate (−14.8 kcal/mol) and Creatine phosphate (−10.3 kcal/mol).
ATP’s intermediate ΔG allows it to _______.
ATP’s intermediate ΔG allows it to both donate and accept phosphate groups.
Substrate-level phosphorylation involves direct transfer of phosphate from _______.
Substrate-level phosphorylation involves direct transfer of phosphate from organic intermediates.
Substrate-level phosphorylation occurs in _______ and accounts for _______.
Substrate-level phosphorylation occurs in glycolysis and TCA cycle and accounts for <10% of total ATP.
Oxidative phosphorylation occurs in _______ and produces _______.
Oxidative phosphorylation occurs in mitochondria and produces >90% of ATP.
Oxidative phosphorylation requires _______ as the final electron acceptor.
Oxidative phosphorylation requires oxygen as the final electron acceptor.
During electron transport, electrons flow from _______ to _______.
During electron transport, electrons flow from NADH and FADH₂ to O₂.
Oxygen has the _______.
Oxygen has the highest reduction potential.
Electron flow drives _______ across the inner mitochondrial membrane, creating a proton gradient known as the _______.
Electron flow drives proton pumping across the inner mitochondrial membrane, creating a proton gradient known as the proton motive force.
The chemiosmotic hypothesis proposed by _______ states that proton gradient energy drives _______.
The chemiosmotic hypothesis proposed by Peter Mitchell states that proton gradient energy drives ATP synthase.
Protons re-enter the matrix via _______, and ATP synthesis is _______.
Protons re-enter the matrix via F₀F₁ ATP synthase, and ATP synthesis is coupled to proton flow.
ATP exits mitochondria via _______ while ADP enters in exchange for _______.
ATP exits mitochondria via ATP–ADP translocase while ADP enters in exchange for ATP.
This transport maintains _______.
This transport maintains continuous ATP synthesis.
The redox free energy equation is given by _______ where n is the number of electrons transferred and F (Faraday constant) ≈ _______.
The redox free energy equation is given by ΔG°′ = −nFΔE°′ where n is the number of electrons transferred and F (Faraday constant) ≈ 23 kcal/mol·V.
Positive ΔE°′ results in _______.
Positive ΔE°′ results in negative ΔG°′.
Reduction potential measures the _______.
Reduction potential measures the tendency to accept electrons.
Oxygen has the _______ and electrons flow from _______.
Oxygen has the highest E°′ and electrons flow from low E°′ to high E°′.
Coupled reactions link an _______ to an _______ requiring a _______.
Coupled reactions link an endergonic reaction to an exergonic reaction requiring a shared intermediate.
Total ΔG must be _______ for the process to proceed.
Total ΔG must be negative for the process to proceed.
Example: Malate → Oxaloacetate (ΔG°′ +7) coupled to Oxaloacetate → Citrate (ΔG°′ −9) results in net ΔG°′ _______.
Example: Malate → Oxaloacetate (ΔG°′ +7) coupled to Oxaloacetate → Citrate (ΔG°′ −9) results in net ΔG°′ negative.
Metabolic pathways are _______, even if individual steps may be _______.
Metabolic pathways are overall spontaneous, even if individual steps may be nonspontaneous.
Directionality in metabolic pathways is determined by _______.
Directionality in metabolic pathways is determined by ΔG, not ΔG°′ alone.
ATP couples _______ and _______ reactions.
ATP couples energy-producing and energy-requiring reactions.
Biological systems cannot extract usable energy from heat diffusion because cellular temperature is higher than the surroundings.
Examples of high-energy phosphate compounds include Phosphoenolpyruvate (−14.8 kcal/mol) and Creatine phosphate (−10.3 kcal/mol).
Substrate-level phosphorylation occurs in glycolysis and TCA cycle and accounts for <10% of total ATP.
Electron flow drives proton pumping across the inner mitochondrial membrane, creating a proton gradient known as the proton motive force.
The chemiosmotic hypothesis proposed by Peter Mitchell states that proton gradient energy drives ATP synthase.
The redox free energy equation is given by ΔG°′ = −nFΔE°′ where n is the number of electrons transferred and F (Faraday constant) ≈ 23 kcal/mol·V.
Coupled reactions link an endergonic reaction to an exergonic reaction requiring a shared intermediate.
Example: Malate → Oxaloacetate (ΔG°′ +7) coupled to Oxaloacetate → Citrate (ΔG°′ −9) results in net ΔG°′ negative.
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